Fire performance of a new shear transfer system for CFST columns

Abstract

The conventional shear transfer elements applied in beam-to-CFST columns include shear studs, steel bars, angles, internal rings, and steel plates. The new UPCCFST system is comparatively easier to execute because the shear transfer elements are provided by simply punching the steel tube. In the first phase of the research, ambient temperature push-out tests were carried out involving 56 test specimens. The shear bond between the concrete core and the steel tube resulted up to 12.31 times greater than the plain CFST system. This paper studies the shear bond in UPCCFST columns exposed to extreme temperatures exceeding 500º. The testing procedure includes pre-loading at ambient temperature, applying a temperature curve up to 530º, and conducting a mechanical push-out test on a total number of 6 specimens. The results show that the average shear bond has improved by 2.08 times compared to the conventional flat CFST specimens. The failure modes, the force-slip relationship, and the concrete strength after the fire tests have also been analyzed.